Geostatistical Mapping of Mountain Precipitation Incorporating Autosearched Effects of Terrain and Climatic Characteristics

Hydrologic and ecologic studies in mountainous terrain are sensitive to the temporal and spatial distribution of precipitation. In this study a geostatistical model, Auto-Searched Orographic and Atmospheric Effects Detrended Kriging (ASOADeK), is introduced to map mountain precipitation using only precipitation gauge data. The ASOADeK model considers both precipitation spatial covariance and orographic and atmospheric effects in estimating precipitation distribution. The model employs gauge data and a multivariate linear regression approach to autosearch regional and local climatic settings (i.e., infer the spatial gradient in atmospheric moisture distribution and the effective moisture flux direction), and local orographic effects (the effective terrain elevation and aspect). The observed gauge precipitation data are then spatially detrended by the autosearched regression surface. The spatially detrended gauge data are further interpolated by ordinary kriging to generate a residual precipitation surface. The precipitation map is then constructed by adding the regression surface to the kriged residual surface. The ASOADeK model was applied to map monthly precipitation for a mountainous area in semiarid northern New Mexico. The effective moisture flux directions and spatial moisture trends identified by the optimal multiple linear regressions, using only gauge data, agree with the regional climate setting. When compared to a common precipitation mapping product [Precipitation-elevation Regression on Independent Slopes Model (PRISM)], the ASOADeK summer precipitation maps of the study area agree well with the PRISM estimates, and with higher spatial resolution. The ASOADeK winter maps improve upon PRISM estimates. ASOADeK gives better estimates than precipitation kriging and precipitation-elevation cokriging because it considers orographic and atmospheric effects more completely.